1. Field of the Invention
The present invention relates to a technique for cooling a battery by blowing air, such as from a cooling fan.
2. Description of the Related Art
Batteries are known to generate Joule heat when being charged or discharged. To prevent an excessive rise in battery temperature due to Joule heat, known battery cooling devices cool batteries by blowing cooling air from a cooling fan.
Japanese Patent Laid-Open Publication No. Hei 9-92347 discloses a battery cooling device for controlling the drive of a cooling fan on the basis of an estimated internal temperature by estimating the internal temperature of a battery on the basis of the surface temperature of the battery and the calorific value of the battery. The battery cooling device in Japanese Patent Laid-Open Publication No. Hei 9-92347 continues to drive the cooling fan until the internal temperature of the battery drops to a predetermined temperature.
Furthermore, Japanese Patent Laid-Open Publication No. Hei 10-64598 discloses a battery cooling device for controlling a cooling fan on the basis of the battery temperature and the battery temperature time change rate. As shown in the cooling fan control maps in FIGS. 4, 8 and 13 in Japanese Patent Laid-Open Publication No. Hei 10-64598, the battery control device in Japanese Patent Laid-Open Publication No. Hei 10-64598 continues to drive the cooling fan if the battery temperature is high even with a low battery temperature time change rate. That is, the battery cooling device in Japanese Patent Laid-Open Publication No. Hei 10-64598 also continues to drive the cooling fan unless the battery temperature drops to a predetermined temperature.
In addition, Japanese Patent Laid-Open Publication No. 2005-63689 discloses a battery cooling control device for controlling a cooling fan on the basis of the battery temperature and the cooling air temperature. The battery cooling control device in Japanese Patent Laid-Open Publication No. 2005-63689 prevents the battery from being cooled more than necessary by reducing the air flow of the cooling fan in the case when the difference between the battery temperature and the cooling air temperature is large and the cooling air temperature is low. However, the battery cooling control device in Japanese Patent Laid-Open Publication No. 2005-63689 also continues to drive the cooling fan unless the battery temperature drops to a predetermined temperature.
Thus, the devices disclosed in the patent documents continue to drive the cooling fan unless the battery temperature drops to a predetermined temperature.